This invention relates to media for preparing duplicates of originals such as printed matter and the like.
There exists a need for a means by which copies of original documents can be made outside the usual business office or copy center at reasonable price. Means for "home-copying" currently available today suffer from shortcomings, such as high cost of apparatus and/or media, and inability to copy from two-sided originals. Home-copiers employing xerographic processes are generally expensive initially and are generally demanding of maintenance.
Workman, U.S. Pat. No. 3,094,417, discloses a method of making a copy of a graphic original having differentially radiation-absorptive image and background areas, comprising (1) placing over and in close contact with said original a light-desensitizable colored light-transmissive intermediate film material comprising a transparent film backing having a uniform bonded face-coating including a first reactant and a colored activatible organic photoreducible dye, (2) exposing the original through said film material to visible light of which at least a significant portion of said light is absorbable by said dye for a time and at an intensity sufficient to cause total desensitization of said first reactant at areas corresponding to the least absorptive areas of the original and significantly less than total desensitization at areas corresponding to the most absorptive areas of the original, (3) placing the thus exposed film material in face-to-face close contact with a receptor sheet comprising a paper-like backing sheet having a bonded face-coating comprising a second reactant inter-reactive with said first reactant to produce a visibly distinct colored reaction product when the reactants are briefly heated together at a conversion temperature within the range of about 90.degree. C. to about 150.degree. C., (4) heating to the conversion temperature to produce on said receptor sheet a visible reproduction of image areas of the original, and (5) separating the receptor sheet and the intermediate film.
The foregoing process calls for the exposed film to be placed with its coated surface in contact with the coated surface of the paper receptor sheet and the composite to be pressed between flat glass panels, previously heated to approximately 110.degree. C., for a few seconds, or alternatively the composite to be passed around a heated bar or between squeeze rolls of which one or both is maintained at the required elevated temperature. It would be desirable, from the standpoint of cost, to eliminate the flat glass panels, squeeze rolls, or the like, in the image-forming steps.
Purdy, U.S. Pat. No. 2,733,994, discloses a process of making photographic duplicate of an original which comprises (1) placing on the surface of the original a transparent film carrying a light-sensitive printing-out emulsion and an overlayer of material having a tacky surface, the tacky surface being in contact with the original, (2) exposing the thus covered original to light through the transparent film, and (3) removing the film from the original. The requirement for good contact during exposure was effected by means of a tacky surface in the absence of pressure plates, vacuum frames, and other cumbersome equipment. This patent suggests the use of gelatin as the best adhesive material to use in this process. It also suggests that glycerin be used with gelatin to give desirable tack. Because the adhesiveness or tack of gelatin, even when fortified with a humectant like glycerin will change with changes in relative humidity, the desired degree of tack cannot be maintained over a sufficient range of atmospheric humidity to produce a useful product. Because gelatin is an excellent culture medium for bacteria and molds and is used as such in the laboratory, it is preferred to keep the moisture content of a gelatin-containing product low in order to prevent microbiological attack, e.g. mildew. At low moisture levels, however, gelatin is insufficiently tacky for adhesive purposes. Furthermore, gelatin is not sufficiently permeable to gases to allow a volatizable reactant to diffuse therethrough in order to react with a second reactant on a receptor sheet.